| Presentation Title: | Close interaction of turbulent convection and magnetic twist in sunspot formation and flare eruptions |
| Author(s): | Shin Toriumi, Hideyuki Hotta, Kanya Kusano |
Abstract:
Magnetic flux emergence from the deep convection zone is a key piece of the global magnetism of the Sun and crucial for the generation of active regions and triggering of jets, flares, and coronal mass ejections. To investigate the effect of thermal convection and magnetic twist to the emergence, we performed radiative magnetohydrodynamic simulations of flux tube emergence from the deep, realistic convection zone, where we controlled the twist strength of the initial flux tube. Contrary to one’s intuition, even in the case of an untwisted flux tube, the generated sunspots inject finite (non-zero) magnetic helicity into the upper atmosphere, because the strong background turbulence rotates the magnetic flux. The amount of total injected helicity due to the turbulence is significant and even explains the medium-sized solar eruptions. We also revealed that the emergence of strongly-twisted flux tube, unstable to the kink instability, produces sunspots with magnetic helicity far exceeding the observed values. Although the kink instability has long been regarded as a prominent candidate for the massively-flaring delta-type sunspots, this result suggests that it is less likely, which calls for further study combining numerical modeling and observational data to better understand the genesis of flare-productive active regions.